The present invention relates to a piezoelectric vibrator unit preferably used to eject ink droplets, and an ink-jet recording head that employs the piezoelectric vibrator unit. In particular, the present invention relates to a piezoelectric vibrator unit and an ink-jet recording head that can suppress bending during the operation of the piezoelectric vibrator.
An ink-jet recording head (hereinafter referred to as a recording head) used for an image recording apparatus, such as an ink-jet printer or plotter, comprises: a flow passage unit, which includes pressure chambers and a reservoir; and a piezoelectric vibrator unit, which is located at the rear of the flow passage unit and which includes a plurality of piezoelectric vibrators for changing the volumes of the associated pressure chambers.
The following procedures, for example, are employed to fabricate the piezoelectric vibrator unit. First, common internal electrodes and segment internal electrodes are alternately laminated with piezoelectric material interposed between the adjacent internal electrodes to thereby form a plate-like laminated member. A common external electrode and a segment external electrode are formed on a surface of the laminated member to be electrically connected to the common internal electrodes and the segment internal electrodes, respectively. Then, one side face of the base end portion of the laminated member having the external electrodes is secured to a fixing plate, and thereafter, the leading end portion of the laminated member is cut into a plurality of extremely narrow piezoelectric vibrators using the a wire saw or a dicing saw.
The piezoelectric vibrator of this type is affected by a constraining force exerted at a joint portion thereof because one side face of the base end portion of the laminated member is secured to the fixing plate. That is, when voltage is applied to the external electrode to cause the piezoelectric vibrator to contract, the piezoelectric material in the opposite side (i.e. the side opposite in the lamination direction from the side where the piezoelectric vibrator is fixed to the fixing plate) tends to contract slightly more than the piezoelectric material in the fixing plate side.
Therefore, as shown in FIG. 9, bending occurs, i.e., the piezoelectric vibrator 200 is bent in the lamination direction away from the fixing plate 204 (upward in FIG. 9).
Due to such bending of the piezoelectric vibrator 200, a pressure wave as denoted by α in FIG. 10 is generated within the pressure chamber 203 of a recording head 202, which repeatedly reflects and reciprocates within the pressure chamber 203 as if the pressure chamber 203 was an acoustic tube. The pressure wave adversely affects ink ejection by generating a mist or a satellite, or by curving the flight path of an ink droplet.
Since no damper element for positively attenuating the pressure wave is present in the pressure chamber 203, it takes a time until the pressure wave is satisfactorily attenuated. Consequently, a required time interval to a next ink droplet ejection is long, hindering the high frequency driving of the piezoelectric vibrator.